Boring ctenostomate bryozoans from the Korytnica Clays (Middle Miocene; Holy Cross Mountains, Central Poland)

An assemblage of boring ctenostomate bryozoans that comprises well developed and preserved colonies of Spatlhipora sp., Terebripora sp., and Penetrantia sp. is recognized in circum-apertural parts of some gastropod shells contained within the Middle Miocene (Badenian) Korytnica Clays exposed on the southern slopes of the Holy Cross Mountains, Central Poland. Taphonomical features of the bryozoan-infected shells evidence the settlement of the bryozoa after the death of the gastropod. The choice of some special gastropod shells by the bryozoans suggests furthermore that taken by the bryzoans became the shells inhabited by the hermit crabs to whom the bryozoans were the commensals. This biologic relationship is discussed in comparison with the other comrnensals to the hermit crabs that have dwelled in the Korytnica basin.